If you have a teenage son or daughter, you've probably spotted them making weird and contorted faces at their smartphone's front-facing camera. They're using Snapchat, a wildly popular photo and video sharing application in which users can send each other snapshots or short recordings that are viewable for anywhere from 1 second to up to 10 seconds (the recipient can always save a screenshot, though the app tattles on them if they do).

It's a simple, free app available on iOS and Android that's quickly approaching a $1 billion valuation. To keep things fresh, and to keep that value up there, the Snapchat team just issued an update that adds a "Stories" feature, which is sort of like having a constantly evolving (and evaporating) Timeline.

"Snapchat Stories add Snaps together to create a narrative. When you add a Snap to your Story it lives for 24 hours before it disappears, making room for the new," Snapchat explains in a blog post. "Your Story always plays forward, because it makes sense to share moments in the order you experience them."

To use the new feature, you take a picture or video and tap the arrow as you normally would, which brings you to your list of Snapchat contacts. However, there's a new entry called "My Story" at the top of the list, and that's what you select to play around with this new feature.

The Snapchat team is so excited about this feature that it's releasing the update simultaneously on iOS and Android for the first time ever.